An example of a conventional structure for mounting a base and a base cover in a door mirror is shown in FIG. 5 which is a sectional view. In FIG. 5, a stand 22 for pivotally supporting a visor (not shown) which is a mirror casing of the door mirror is fixed to a base 21 by means of a mounting screw 23 being inserted into the base 21 from a lower side thereof. In this structure, a projection part 25 of the base 21 is fitted in a concave part 26 of a base cover 24 by covering the base cover 24 onto the base 21 from a right side in the figure.
In this structure, the engaging part of the base cover 24 is mounted thereon by a loose fit therebetween in assembling, and the base cover 24, which is a plastic molding product, is liable to deform by heat at time of painting. Therefore, there is a possibility that the upper surface of the base cover 24 is not flush with the upper surface of the stand 22 when the base cover 24 is mounted on the base 21. Also, in this structure, there is a gap which is formed between a head part of the mounting screw 23 and a hole 27 of the base cover 24. Therefore, the gap becomes an entrance and exit of air, so that an air-striking sound is caused thereby.
On the other hand, FIG. 6 shows another example of a mounting structure. In this structure, a base cover 33 is mounted on a base 31 by means of a mounting screw 34 when a stand 32 is fixed to the base 31, so that the base cover 33 and the stand 32 are fixed to the base 31 simultaneously by the mounting screw 34. As a mounting portion, the base 31 has a boss 35 having a surface which is a bit retracted inwardly with respect to an upper surface of the base cover 33. After the base cover 33 is fitted in the boss 35, the mounting screw 34 is tightened through a plain washer 36 and a spring washer 37.
With the structure, it is possible not only to allow the upper surface of the base cover 33 to be flush with the upper surface of the stand 32 by correcting the deformation of the base cover 33, but also to prevent the generation of the air-striking sound. However, because the base cover 33 is installed on the base 31 with the pair of washers 36 and 37 being sandwiches therebetween, the head of the mounting screw 34 is positioned lower by the thickness corresponding thereto than the mounting screw shown in FIG. 5. Therefore, in order to hide the head of the mounting screw 34 from view, it is necessary to lower the lower surface of the base cover 33 up to a position as shown by an imaginary line. As a result, the thickness of the stay increases.
Accordingly, it is difficult to simultaneously satisfy, with the conventional arts, all of the three objects of: correcting the deformation of the base cover, preventing the generation of the air whistling sound, and preventing the increase in thickness of the stay.